Hardness refers to the ability of a material to resist the pressure of a hard object being pressed into its surface. It is of the important performance indexes of metallic materials. Generally, the higher the hardness, the better the abrasion resistance. The commonly used hardness indexes are Brinell hardness, Rock hardness and Vickers hardness. Let's take a look at the common hardness indexes of the hardness tester with Zijin.

1. Vickers hardness

Vickers hardness (HV) is pressed into the surface of the material with a diamond square cone press with a top angle of 136 degrees and a load of than 120 kg. The surface area of the material impression pit is divided by the load value, which is the Vickers hardness HV value (kgf/mm2)

Brinell hardness (HB) is pressed into the surface of the material with a hardened steel ball of a certain size (the diameter is usually 10 mm at a certain load (usually 3000 kg), and kept for a period of time. After unloading, the ratio of the load to the area of its is the Brinell hardness value (HB), and the unit is kilogram force/mm2 (N/mm2).

2. Rockwell

Rockwell hardness (HR) cannot be used if HB > 450 or the sample is too small, and Rockwell hardness should be used instead. a certain load, a diamond cone with a top angle of 120 degrees or a steel ball with a diameter of 1.59 mm and 3.1 mm is pressed into the surface of the material to be tested, and the hardness of the material is calculated according to the depth of indentation. According to the different hardness of the tested, it can be expressed by three different levels:

HRA: Hardness obtained by using a load of 60 kg and a diamond punch, used materials with higher hardness (such as cemented carbide, etc.).

HRB: Hardness of steel ball hardened at 100 kg load and1.58 mm diameter. It is used for materials with low hardness (such as annealed steel and cast iron, etc.).

HRC: Hardness obtained using a load of 150 kg and a diamond punch, used for materials with high hardness (such as hardened steel, etc.)